1. Field of the Invention
This invention relates to a picking head assembly suitable for incorporation in an automated mushroom harvesting apparatus, as well as to methods of operating such a picking head assembly. The invention further relates to an automated mushroom harvesting apparatus whenever incorporating a picking head assembly of this invention, and to methods of operating such automated mushroom harvesting apparatus.
2. Description of the Prior Art
The growing and harvesting of mushrooms--and particularly of the species agaricus--on a commercial scale is a most labour-intensive industry, in which approximately 75% of the work-force is engaged in the process of harvesting (picking) the growing maturing fruit bodies (mushrooms). In many countries, there is an increasing demand for commercially-produced mushrooms but, on account of the labour-intensive nature of the business, it is difficult for producers to keep pace with the demand. Mushroom picking is generally low-level poorly-paid work and the labour turnover rates tend to be high. If therefore the picking process could be automated, the industry would obviously benefit.
The automated picking of mushrooms is hampered by the difficulty that mushrooms bruise easily and then discolour, or--if the mushrooms are subjected to slightly greater forces--the mushrooms tend to break apart or separate from their stalks. Preliminary trials with devices intended to assist the automated picking of mushrooms have shown a marked tendency to bruise or otherwise damage large numbers of the mushrooms and it has therefore become apparent that an economically-viable design of automatic mushroom harvester requires the provision of a picking head assembly able to operate at a high speed but which will damage only relatively few mushrooms.
Research work directed at minimising the damage when picking mushrooms automatically has shown that relatively low energy levels must be used at the moment when contact is established between a picking head and a selected mushroom. However, if the picking head is arranged to approach and contact a selected mushroom at a very low speed, to minimise the impact energy, the overall speed of the operation of the automated harvester will be very low and so only relatively few mushrooms will be picked within a given time, as compared to a manual picker. Moreover, complex control mechanisms must be provided to determine the precise position, relative to some datum, of the surface of the mushroom to be contacted by the picking head, because the height of growing mushrooms is so variable, in order that the approach speed of the picking head may suitably be reduced to a sufficiently low value just before contact takes place. This further complication reduces the reliability and increases the likelihood of damage to mushrooms, as well as further reducing the operating speed of the harvester.